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openwrt/target/linux/ath79/patches-5.4/0061-tty-serial-ar933x-uart-rs485-gpio.patch
David Bauer 9dc15e36c8 ath79: drop upstreamed patch 
This patch was backported to the 5.4 kernel tree as commit
c2d5c4df27e0 at least since release v5.4.28. Since then, it enables RX
an TX ready override twice.

Signed-off-by: David Bauer <mail@david-bauer.net>
2021-01-01 19:14:06 +01:00

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From patchwork Fri Feb 21 21:23:31 2020
Content-Type: text/plain; charset="utf-8"
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Content-Transfer-Encoding: 7bit
X-Patchwork-Submitter: Daniel Golle <daniel@makrotopia.org>
X-Patchwork-Id: 1198835
Date: Fri, 21 Feb 2020 22:23:31 +0100
From: Daniel Golle <daniel@makrotopia.org>
To: linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Jiri Slaby <jslaby@suse.com>, Petr =?utf-8?q?=C5=A0tetiar?= <ynezz@true.cz>,
Chuanhong Guo <gch981213@gmail.com>, Piotr Dymacz <pepe2k@gmail.com>
Subject: [PATCH v2] serial: ar933x_uart: add RS485 support
Message-ID: <20200221212331.GA21467@makrotopia.org>
MIME-Version: 1.0
Content-Disposition: inline
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
Emulate half-duplex operation and use mctrl_gpio to add support for
RS485 tranceiver with transmit/receive switch hooked to RTS GPIO line.
This is needed to make use of the RS485 port found on Teltonika RUT955.
Signed-off-by: Daniel Golle <daniel@makrotopia.org>
---
v2: use bool to indicate ongoing half-duplex send, use it afterwards
to decide whether we've just been in a send operation.
drivers/tty/serial/Kconfig | 1 +
drivers/tty/serial/ar933x_uart.c | 113 +++++++++++++++++++++++++++++--
2 files changed, 108 insertions(+), 6 deletions(-)
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig
@@ -1280,6 +1280,7 @@ config SERIAL_AR933X
tristate "AR933X serial port support"
depends on HAVE_CLK && ATH79
select SERIAL_CORE
+ select SERIAL_MCTRL_GPIO if GPIOLIB
help
If you have an Atheros AR933X SOC based board and want to use the
built-in UART of the SoC, say Y to this option.
--- a/drivers/tty/serial/ar933x_uart.c
+++ b/drivers/tty/serial/ar933x_uart.c
@@ -13,6 +13,7 @@
#include <linux/console.h>
#include <linux/sysrq.h>
#include <linux/delay.h>
+#include <linux/gpio/consumer.h>
#include <linux/platform_device.h>
#include <linux/of.h>
#include <linux/of_platform.h>
@@ -29,6 +30,8 @@
#include <asm/mach-ath79/ar933x_uart.h>
+#include "serial_mctrl_gpio.h"
+
#define DRIVER_NAME "ar933x-uart"
#define AR933X_UART_MAX_SCALE 0xff
@@ -47,6 +50,8 @@ struct ar933x_uart_port {
unsigned int min_baud;
unsigned int max_baud;
struct clk *clk;
+ struct mctrl_gpios *gpios;
+ struct gpio_desc *rts_gpiod;
};
static inline unsigned int ar933x_uart_read(struct ar933x_uart_port *up,
@@ -100,6 +105,18 @@ static inline void ar933x_uart_stop_tx_i
ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);
}
+static inline void ar933x_uart_start_rx_interrupt(struct ar933x_uart_port *up)
+{
+ up->ier |= AR933X_UART_INT_RX_VALID;
+ ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);
+}
+
+static inline void ar933x_uart_stop_rx_interrupt(struct ar933x_uart_port *up)
+{
+ up->ier &= ~AR933X_UART_INT_RX_VALID;
+ ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);
+}
+
static inline void ar933x_uart_putc(struct ar933x_uart_port *up, int ch)
{
unsigned int rdata;
@@ -125,11 +142,21 @@ static unsigned int ar933x_uart_tx_empty
static unsigned int ar933x_uart_get_mctrl(struct uart_port *port)
{
- return TIOCM_CAR;
+ struct ar933x_uart_port *up =
+ container_of(port, struct ar933x_uart_port, port);
+ int ret = TIOCM_CTS | TIOCM_DSR | TIOCM_CAR;
+
+ mctrl_gpio_get(up->gpios, &ret);
+
+ return ret;
}
static void ar933x_uart_set_mctrl(struct uart_port *port, unsigned int mctrl)
{
+ struct ar933x_uart_port *up =
+ container_of(port, struct ar933x_uart_port, port);
+
+ mctrl_gpio_set(up->gpios, mctrl);
}
static void ar933x_uart_start_tx(struct uart_port *port)
@@ -140,6 +167,37 @@ static void ar933x_uart_start_tx(struct
ar933x_uart_start_tx_interrupt(up);
}
+static void ar933x_uart_wait_tx_complete(struct ar933x_uart_port *up)
+{
+ unsigned int status;
+ unsigned int timeout = 60000;
+
+ /* Wait up to 60ms for the character(s) to be sent. */
+ do {
+ status = ar933x_uart_read(up, AR933X_UART_CS_REG);
+ if (--timeout == 0)
+ break;
+ udelay(1);
+ } while (status & AR933X_UART_CS_TX_BUSY);
+
+ if (timeout == 0)
+ dev_err(up->port.dev, "waiting for TX timed out\n");
+}
+
+static void ar933x_uart_rx_flush(struct ar933x_uart_port *up)
+{
+ unsigned int status;
+
+ /* clear RX_VALID interrupt */
+ ar933x_uart_write(up, AR933X_UART_INT_REG, AR933X_UART_INT_RX_VALID);
+
+ /* remove characters from the RX FIFO */
+ do {
+ ar933x_uart_write(up, AR933X_UART_DATA_REG, AR933X_UART_DATA_RX_CSR);
+ status = ar933x_uart_read(up, AR933X_UART_DATA_REG);
+ } while (status & AR933X_UART_DATA_RX_CSR);
+}
+
static void ar933x_uart_stop_tx(struct uart_port *port)
{
struct ar933x_uart_port *up =
@@ -153,8 +211,7 @@ static void ar933x_uart_stop_rx(struct u
struct ar933x_uart_port *up =
container_of(port, struct ar933x_uart_port, port);
- up->ier &= ~AR933X_UART_INT_RX_VALID;
- ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);
+ ar933x_uart_stop_rx_interrupt(up);
}
static void ar933x_uart_break_ctl(struct uart_port *port, int break_state)
@@ -336,11 +393,20 @@ static void ar933x_uart_rx_chars(struct
static void ar933x_uart_tx_chars(struct ar933x_uart_port *up)
{
struct circ_buf *xmit = &up->port.state->xmit;
+ struct serial_rs485 *rs485conf = &up->port.rs485;
int count;
+ bool half_duplex_send = false;
if (uart_tx_stopped(&up->port))
return;
+ if ((rs485conf->flags & SER_RS485_ENABLED) &&
+ (up->port.x_char || !uart_circ_empty(xmit))) {
+ ar933x_uart_stop_rx_interrupt(up);
+ gpiod_set_value(up->rts_gpiod, !!(rs485conf->flags & SER_RS485_RTS_ON_SEND));
+ half_duplex_send = true;
+ }
+
count = up->port.fifosize;
do {
unsigned int rdata;
@@ -368,8 +434,14 @@ static void ar933x_uart_tx_chars(struct
if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
uart_write_wakeup(&up->port);
- if (!uart_circ_empty(xmit))
+ if (!uart_circ_empty(xmit)) {
ar933x_uart_start_tx_interrupt(up);
+ } else if (half_duplex_send) {
+ ar933x_uart_wait_tx_complete(up);
+ ar933x_uart_rx_flush(up);
+ ar933x_uart_start_rx_interrupt(up);
+ gpiod_set_value(up->rts_gpiod, !!(rs485conf->flags & SER_RS485_RTS_AFTER_SEND));
+ }
}
static irqreturn_t ar933x_uart_interrupt(int irq, void *dev_id)
@@ -427,8 +499,7 @@ static int ar933x_uart_startup(struct ua
AR933X_UART_CS_TX_READY_ORIDE | AR933X_UART_CS_RX_READY_ORIDE);
/* Enable RX interrupts */
- up->ier = AR933X_UART_INT_RX_VALID;
- ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);
+ ar933x_uart_start_rx_interrupt(up);
spin_unlock_irqrestore(&up->port.lock, flags);
@@ -511,6 +582,21 @@ static const struct uart_ops ar933x_uart
.verify_port = ar933x_uart_verify_port,
};
+static int ar933x_config_rs485(struct uart_port *port,
+ struct serial_rs485 *rs485conf)
+{
+ struct ar933x_uart_port *up =
+ container_of(port, struct ar933x_uart_port, port);
+
+ if ((rs485conf->flags & SER_RS485_ENABLED) &&
+ !up->rts_gpiod) {
+ dev_err(port->dev, "RS485 needs rts-gpio\n");
+ return 1;
+ }
+ port->rs485 = *rs485conf;
+ return 0;
+}
+
#ifdef CONFIG_SERIAL_AR933X_CONSOLE
static struct ar933x_uart_port *
ar933x_console_ports[CONFIG_SERIAL_AR933X_NR_UARTS];
@@ -680,6 +766,8 @@ static int ar933x_uart_probe(struct plat
goto err_disable_clk;
}
+ uart_get_rs485_mode(&pdev->dev, &port->rs485);
+
port->mapbase = mem_res->start;
port->line = id;
port->irq = irq_res->start;
@@ -690,6 +778,7 @@ static int ar933x_uart_probe(struct plat
port->regshift = 2;
port->fifosize = AR933X_UART_FIFO_SIZE;
port->ops = &ar933x_uart_ops;
+ port->rs485_config = ar933x_config_rs485;
baud = ar933x_uart_get_baud(port->uartclk, AR933X_UART_MAX_SCALE, 1);
up->min_baud = max_t(unsigned int, baud, AR933X_UART_MIN_BAUD);
@@ -697,6 +786,18 @@ static int ar933x_uart_probe(struct plat
baud = ar933x_uart_get_baud(port->uartclk, 0, AR933X_UART_MAX_STEP);
up->max_baud = min_t(unsigned int, baud, AR933X_UART_MAX_BAUD);
+ up->gpios = mctrl_gpio_init(port, 0);
+ if (IS_ERR(up->gpios) && PTR_ERR(up->gpios) != -ENOSYS)
+ return PTR_ERR(up->gpios);
+
+ up->rts_gpiod = mctrl_gpio_to_gpiod(up->gpios, UART_GPIO_RTS);
+
+ if ((port->rs485.flags & SER_RS485_ENABLED) &&
+ !up->rts_gpiod) {
+ dev_err(&pdev->dev, "lacking rts-gpio, disabling RS485\n");
+ port->rs485.flags &= ~SER_RS485_ENABLED;
+ }
+
#ifdef CONFIG_SERIAL_AR933X_CONSOLE
ar933x_console_ports[up->port.line] = up;
#endif
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